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All You Need to Know About a Downspout Extension

Rimlee Bhuyan Dec 11, 2018
A downspout extension carries the rainwater that drains through the downspout pipe, away from the house. It is a very important drainage system method. Here is the procedure to install it.
A good drainage system keeps your yard or garden dry by channeling water away from it and preventing its stagnation. A downspout drainage is one of the most essential drainage systems. A downspout is a vertical length of pipe connected to the rain gutters that are attached to the roof.
It allows water collected on the roof, to flow through and seep into the ground. A dry well or underground drainage system is connected to the exit point of the pipe. If the water exits at a location very near to the house, it can damage the house's foundation. Many home owners face this problem. It can be solved by having a downspout extension.

Installation Process

Most homes do not have a proper exit point for the downspout pipe, which causes the rainwater to exit into the yard, very close to the house. In the long run, it becomes a potentially dangerous situation as it weakens the foundation of the house, makes the yard mushy, and can even cause water seepage in the basement.
The best way to avoid these problems is installing a downspout extension. It can be done in two ways-by installing above-ground or below-ground extension. Above-ground extensions are unsightly, and may cause someone tripping over. It is better to have below-ground extensions. The process is same as drainage pipe installation, simple, but time-consuming.

Items Required

  • PVC pipe (4 inch diameter)
  • Flexible plastic drainpipe (4 inch diameter)
  • Cement
  • PVC primer
  • Downspout adapter
  • Shovel
  • Hacksaw
  • Measuring tape
  • Elbow joints


The first step is to mark the area of the ground under which the extension will be installed. Once you prepare the basic layout, start digging the marked area, starting from the point where water exits the original downspout pipe. The depth of the trench should be around 10 inches, and the width 6 inches.  It should slope 1 to 2 inches downward.
Install the downspout adapter and coupling at the bottom of the pipe using the zip screws. Make sure that the adapter is firmly in place. Next, place a 90-degree elbow joint in the trench, such that it is positioned directly under the coupling.
Measure the length between the 90-degree elbow joint and coupling with a tape measure. Cut a piece of the PVC pipe of the same measurement with the hacksaw. Apply primer on both ends of the pipe, followed by cement, and then join each pipe end to the coupling and elbow joint respectively.
Cut another length of pipe to fit the length of the trench, and attach one end to the elbow joint with the primer and cement. On reaching the other end of the trench, the installation process is complete. After you are done, fill the trench with sand and soil to hold the pipe in place. Make sure that the extension exits into a dry well or rain barrel.
If you want to prevent water logging in your yard and save your house from foundation damage, then you should consider installing this drainage system on your property.